Multiple Myeloma in Dogs: What It Is and How To Help Your Pet

Multiple myeloma in dogs is a rare type of blood cancer that develops in plasma cells, a type of white blood cell that helps the immune system fight infection. While the disease can affect many parts of the body—including the bones, kidneys, and blood—it often responds well to treatment when diagnosed early. 

Because symptoms can be vague and develop slowly, multiple myeloma may go unnoticed for months or even years. Understanding the signs, causes, diagnosis, and treatment options can help pet parents recognize potential concerns and work with their veterinarian to provide the best possible care. 

What Is Multiple Myeloma in Dogs?

Multiple myeloma in dogs is a rare type of blood cancer that can develop in plasma cells, which are white blood cells that make antibodies to help your dog’s body fight off germs that can cause them to get sick. Plasma cells are found in bone marrow, the spongy material in the center of your dog’s bones. 

Plasma cells that become cancerous make abnormal antibodies that can hurt your dog. These cancerous plasma cells build up faster than healthy plasma cells and eventually become the main type of plasma in your dog’s bone marrow. Multiple myeloma typically starts in multiple places within the bone marrow. 

The abnormal antibodies coming from cancerous plasma cells can make their way to other organs in the body such as the kidneys. This can cause these organs to not function properly. 

Symptoms of Multiple Myeloma in Dogs

While symptoms may take years to appear, common signs of multiple myeloma in dogs include: 

• Signs of pain, such as more sensitivity to touch 

• Lameness 

• Weight loss 

• Abnormally low numbers of white blood cells and blood platelets (seen in their blood work) 

• Abnormally high levels of calcium in the blood (seen in their blood work) 

• Reluctance to stand or walk 

• Kidney failure 

• Heart disease 

Causes of Multiple Myeloma in Dogs

There is no single known cause for multiple myeloma in dogs. 

Exposure to chemicals, constant activation of the immune system, illness from a viral infection, and genetics are all suspected to play a role. 

Carcinogens, like secondhand cigarette smoke, pesticides and radon, all can increase a dog’s risk for multiple myeloma. 

Though not well understood, some breeds have higher rates of multiple myeloma in dogs. These include: 

• Giant Schnauzer 

• Labrador Retriever 

• Golden Retriever 

• German Shepherd  

Gender does not seem to be a risk factor for multiple myeloma. 

As with most other cancers, older dogs are more likely to be affected by the disease. The average age of diagnosis for multiple myeloma is 8–9 years of age. 

How Veterinarians Diagnose Multiple Myeloma in Dogs

Multiple myeloma in dogs is very rare and makes up less than 1% of all cancers in dogs, so it may not be the first suspected cause of your dog’s symptoms. 

Your dog’s vet will start with an exam and then likely recommend blood work and X-rays. 

If there are changes in these tests that are suspicious for multiple myeloma, like elevated globulins in the blood or bone loss on X-rays, the following tests may be recommended: 

• Computed tomography (CT) scan: This test will help the vet better see your dog’s bones. Bones with a “patchy” appearance may be damaged, which is a common clinical sign of multiple myeloma. 

• Bone marrow aspirate: This test involves taking a sample of your dog’s bone marrow to find out if there are too many plasma cells indicating multiple myeloma. This is done in sterile conditions with your pup under anesthesia. A special needle is used. 

• Special urine testing: Your veterinarian may send your dog’s urine off to a lab to figure out the level of Bence-Jones proteins present. Bence-Jones proteins are a type of antibody. High levels of these in urine is a sign of multiple myeloma. 

Cancer staging is part of diagnosis that can determine how far your dog’s cancer has spread and advanced.  

Your vet may recommend that you take your dog to see an oncologist to aid in staging and treatment of the disease.    

Treatment of Multiple Myeloma in Dogs

Treatment for multiple myeloma in dogs includes chemotherapy as the first choice of treatment. 

Approximately 80%–95% of dogs diagnosed with multiple myeloma benefit from chemotherapy within three to six weeks. 

 Oral chemotherapy medications that may be prescribed include: 

• Melphalan (most used with a corticosteroid called prednisone) 

• Chlorambucil and cyclophosphamide (may be prescribed either alone or together) 

• Doxorubicin (most often used for relapses and may be used with another chemotherapy drug, vincristine) 

Radiation can also help to treat multiple myeloma and ease bone pain to make your dog more comfortable. 

Fluid therapy may be suggested to make sure your dog is hydrated and has the right level of electrolytes. This can be especially helpful for dogs with kidney failure due to multiple myeloma. 

Anti-inflammatory medicines, such as corticosteroids like prednisone or dexamethasone, may be prescribed to help reduce swelling. 

Inflammation is an important natural reaction to injury and infection in the body, but too much inflammation can be painful and can damage healthy cells.  

Furosemide is a medication that can help reduce inflammation in the bladder in dogs on the chemo medication cyclophosphamide. 

It can be particularly helpful for dogs with kidney failure and heart disease due to their multiple myeloma. 

Bisphosphonates, such as pamidronate, may be incorporated into your dog’s treatment plan as well. These can be useful for stopping the breakdown of bone cells, which helps to decrease the level of calcium in your dog’s blood, ultimately improving their bone condition and relieving pain. 

Recovery and Management of Multiple Myeloma in Dogs

Multiple myeloma in dogs is rarely cured, and dogs who achieve remission are expected to relapse. 

Fortunately, multiple myeloma is manageable so long as your dog is checked by their veterinarian often. This means that regularly scheduled blood work and examinations by a veterinarian will be needed. Usually, these visits are recommended every two to four weeks initially after starting treatment, then spread out to every two to three months. 

Doing things that help to keep your dog otherwise healthy and comfortable while they are living with the disease can help. 

For example, your dog’s veterinarian may suggest feeding them a well-balanced diet low in carbohydrates and high in omega-3 fatty acids, giving them a daily multivitamin to ensure their nutritional needs are met, or administering medication as prescribed to control their pain levels. 

Talk to your veterinarian to help you figure out which practices may be best for your dog.